International Concrete Abstracts Portal

Corrosion of steel reinforcement is one of the primary contributing factors to bridge deck deterioration. Based on the extent of corrosion, different corrosion mitigation strategies can be used to extend the service life of a bridge deck. Bridge deck overlays are efficient tools in reducing active corrosion. While there are multiple overlay solutions that are commonly deployed, including concrete-based and polymer-based systems, ultra-high performance concrete (UHPC) overlays have gained interest from bridge owners in recent years. Another corrosion mitigation strategy is the application of corrosion-inhibiting chemicals and sealers to a concrete surface to reduce the ingress of deleterious ions. The purpose of this paper is to compare different corrosion mitigation strategies and study the effects of such techniques on the bond between the UHPC overlay and the substrate concrete. UHPC overlays were found to be effective in reducing corrosion rates by more than 50 percent. Sealers and corrosion inhibitors applied to the concrete substrate in combination with placing a UHPC overlay reduced the corrosion rates even further. However, sealers and corrosion inhibitors appeared to negatively affect bond strength, potentially increasing the likelihood of overlay delamination.

Using particle packing models (PPMs) in combination with limestone fillers has been shown to be effective in proportioning eco-efficient concrete mixtures with reduced Portland cement content, resulting in suitable performance in fresh and short-term hardened states. However, the decrease in Portland cement and increase in limestone fillers may lower the pH of concrete, raising concerns about durability and long-term performance, potentially leading to increased corrosion of steel reinforcement in the presence of carbonation or chlorides. In this study, the performance of three eco-efficient concrete mixtures with varying cement (250, 200, and 150 kg/m³) and inert filler contents is evaluated against accelerated chloride exposure. The findings highlight the influence of the mixture proportioning and water-to-cement ratio on the resistance to chloride ingress. Ultimately, it is verified that the distance between cement particles is a major contribution towards chloride ingress.

The 16th International Symposium on Fiber-Reinforced Polymer (FRP) Reinforcement for Concrete Structures (FRPRCS-16) was organized by ACI Committee 440 (Fiber-Reinforced Polymer Reinforcement) and held on March 23 and 24, 2024, at the ACI Spring 2024 Convention in New Orleans, LA. FRPRCS-16 gathers researchers, practitioners, owners, and manufacturers from the United States and abroad, involved in the use of FRPs as reinforcement for concrete and masonry structures, both for new construction and for strengthening and rehabilitation of existing structures. FRPRCS is the longest running conference series on the application of FRP in civil construction, commencing in Vancouver, BC, in 1993. FRPRCS has been one of the two official conference series of the International Institute for FRP in Construction (IIFC) since 2018 (the other is the CICE series). These conference series rotate between Europe, Asia, and the Americas, with alternating years between CICE and FRPRCS. The ACI convention has previously cosponsored the FRPRCS symposium in Anaheim (2017), Tampa (2011), Kansas City (2005), and Baltimore (1999). This Special Publication contains a total of 52 peer-reviewed technical manuscripts from 20 different countries from around the world. Papers are organized in the following topics: (1) FRP Bond and Anchorage in Concrete Structures; (2) Strengthening of Concrete Structures using FRP Systems; (3) FRP Materials, Properties, Tests and Standards; (4) Emerging FRP Systems and Successful Project Applications; (5) FRP-Reinforced Concrete Structures; (6) Advances in FRP Applications in Masonry Structures; (7) Seismic Resistance of FRP-Reinforced/Strengthened Concrete Structures; (8) Behavior of Prestressed Concrete Structures; (9) FRP Use in column Applications; (10) Effect of Extreme Events on FRP-Reinforced/Strengthened Structures; (11) Durability of FRP Systems; and (12) Advanced Analysis of FRP Reinforced Concrete Structures. The breadth and depth of the knowledge presented in these papers is clear evidence of the maturity of the field of composite materials in civil infrastructure. The ACI Committee 440 is witness to this evolution, with its first published ACI CODE-440.11, “Building Code Requirements for Structural Concrete with Glass Fiber Reinforced Polymer (CFRP) Bars,” published in 2022. A second code document on fiber reinforced polymer for repair and rehabilitation of concrete is under development. The publication of the sixteenth volume in the symposium series could not have occurred without the support and dedication of many individuals. The editors would like to recognize the authors who diligently submitted their original papers; the reviewers, many of them members of ACI Committee 440, who provided critical review and direction to improve these papers; ACI editorial staff who guided the publication process; and the support of the American Concrete Institute (ACI) and the International Institute for FRP in Construction (IIFC) during the many months of preparation for the Symposium.

This study explores technological advancements enabling the utilization of GFRP bars in concrete structures, particularly in coastal areas. However, GFRP bars often encounter reduced bend strength at specific bend locations, which may pose a challenge in their practical application. Various properties such as the strength of bent GFRP bars are crucial for quality assurance, yet existing testing methods stated in ASTM D7914M-21 and ACI 440.3R-15 have limitations when applied to different GFRP bent shapes. Furthermore, those methods require special precautions to ensure symmetry and avoid eccentricities in specimens. To address these challenges, CSA S807:19 introduced a simpler standardized testing procedure that involves embedding a single L-shaped GFRP stirrup in a concrete block. However, the specified large block size in CSA S807:19 Annex E may pose difficulties for both laboratory and on-site quality control tests. Therefore, CSA S807:19 Annex E (Clause 7.1.2b) permits the use of a customized block size, as long as it meets the bend strength of the FRP bars without causing concrete splitting. To date, very few prior research has explored the use of custom block sizes. Therefore, this study aims to thoroughly investigate the strength of bent FRP bars with custom block sizes and without block confinement. Such an investigation serves to highlight the user-friendliness and efficiency of the CSA S807:19 Annex E method. The study recommends two block sizes: 200x400x300 mm (7.87x15.75x11.81 in) for bars <16 mm (0.63 in) diameter and 200x200x300 mm (7.87x7.87x11.81 in) for bars <12 mm (0.39 in). Additionally, the study cautions against using confinement reinforcement, especially with smaller blocks, as it could interfere with the embedded bent FRP bar. Furthermore, the study suggests incorporating additional tail length to mitigate the debonding effects resulting from fixing the strain gauges to the bent portion of the embedded FRP bar. By exploring these modifications, the study seeks to enhance the effectiveness of the testing procedure and expand its practical application for both laboratory and on-site quality assurance. The findings hold implications for the reliable testing of GFRP bars' strength, advancing their use as reinforcement in concrete structures.

Most of the research related to interface shear transfer in concrete elements has utilized steel bars as reinforcement, while GFRP reinforcement has received little attention experimentally and analytically. For this reason, only a few design specifications include provisions for the calculation of the interface shear transfer when using GFRP. In this project, an experimental campaign is being conducted to determine the contribution of GFRP bars to the mechanism of shear transfer by using push-off specimens. The literature review and the test methodology are reported in this paper. The obtained results indicate that the use of GFRP reinforcement significantly enhances the interface shear strength, resulting in a capacity that exceeds those of the specimens without reinforcement. When the GFRP-reinforced specimen reaches the first crack at a load similar to that of the unreinforced specimens, it continues carrying load until it reaches a peak, thus indicating that the reinforcement is providing both dowel action and clamping force prior the shear failure. Additionally, once the peak strength is reached, the use of GFRP reinforcement allows the specimen to deform in a pseudo-ductile fashion thus preventing sudden failure.